The present invention relates to gas turbine engines, and more particularly, to an epicyclic gear system for use in gas turbine engines.
Epicyclic gear trains are complex mechanisms for reducing or increasing the rotational speed between two rotating shafts or rotors. The compactness of planetary or star system gear trains makes them appealing for use in aircraft engines.
The forces and torque transferred through an epicyclic gear train place tremendous stresses on the gear train components, making them susceptible to breakage and wear. However, imperfect alignment of the longitudinal axes of an epicyclic gear train's sun gear, star gear, and ring gear with an input shaft is common due to numerous factors including imbalances in rotating hardware, manufacturing imperfections, and transient flexure of shafts and support frames due to aircraft maneuvers. This misalignment necessitates increased amounts of lubrication (i.e. to form an adequate film thickness) between each journal bearing and interfacing star gear than would otherwise be necessary. Additionally, this misalignment increases the amount of wear experienced by the journal bearing and interfacing star gear. Thus, there is a need for an epicyclic gear system that can accommodate misalignment with a lower degree of wear.